1. Field of the Invention
The present invention relates to a photoreceptor, and more particularly to a photoreceptor (e.g., an electrophotographic photoreceptor) having a photosensitive layer comprising a carrier generating layer and a carrier transport layer.
2. Description of the Prior Art
Those conventionally known electrophotographic photoreceptors are of the construction comprising in combination a carrier generating layer (hereinafter may be abbreviated to "CGL") containing a carrer generating material (hereinafter may be abbreviated to "CGM") which absorbs visible rays to generate a charge carrier (hereinafter called simply "carrier") and a carrier transport layer (hereinafter may be abbreviated to "CTL") containing a carrier transport material (hereinafter may be abbreviated to "CTM") which transports either a negative carrier or a positive carrier or both carriers that have been generated in the CGL. Allotting in this way the necessary two different basic functions, the carrier generation and the transport thereof, to the separate layers, respectively, that constitutes a photosensitive layer not only extends the selectable range of materials applicable to the construction of the photosensitive layer but also permits the independent selection of the respective materials or types of materials capable of most effectively attaining the respective functions. Also, the above allotment enables the obtaining of an electrophotographic photoreceptor having characteristics required in the electrophotographic process, e.g., such excellent characteristics consisting of high surface electric potential obtained when charged, high charge retainability, high sensitivity to light, and high stability in the repeated use.
As the above photosensitive layer, for example, those of the following constructions are known:
(1) A construction comprising in combination a CGL containing amorphous selenium or cadminum sulfide and a CTL containing poly-N-vinyl carbazole.
(2) A construction comprising in combination a CGL containing amorphous selenium or cadmium sulfide and a CTL containing 2,4,7-trinitrilo-9-fluorenone.
(3) A construction comprising in combination a CGL containing a perylene derivative and a CTL containing an oxadiazole derivative (as disclosed in U.S. Pat. No. 3,871,882).
(4) A construction comprising in combination a CGL containing chlorodianeblue or methyl skaririum and a CTL containing a pyrazoline derivative (Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) No. 90827/1976).
(5) A construction comprising in combination a CGL containing amorphous selenium or an alloy thereof and a CTL containing a polyarylalkane-type aromatic amino compound (Japanese Patent Application No. 147251/1977).
(6) A construction comprising in combination a CGL containing a perylene derivative and a CTL containing a polyarylalkane-type aromatic amino compound (Japanese Patent Application No. 907/1978).
Attempts have been made to obtain an electrophotographic photoreceptor having excellent electrophotographic characteristics and excellent layer strength through the combined use of a low-molecular-weight organic compound as the charge transport material, an arbitrary charge generating material, and a high-molecular binder.
As the above high-molecular binder, polycarbonate is excellent in respect of the chargeability, repeatability, etc., the polycarbonate including, for example, those having the following structural formula unit: ##STR2##
The polycarbonate is of the structure wherein two methyl groups are symmetrically combined to the center carbon atom of bisphenol A. As a result of our additional investigation, however, it has now been found that, if the above polycarbonate is used to form a layer, a crystalline polycarbonate is deposited thereon during the layer formation to tend to cause protruded portions over the formed layer, the protruded portions producing trail marks in the coating to thereby decrease its yield or causing, when the carbonate is used as a photoreceptor, toner residue to remain uncleared at the protruded portions which tends to result in image troubles due to the so-called toner filming. The deposition of the crystalline polycarbonate is considered to result from the fact that, in the above polycarbonate, the groups coupled to the center carbon atom are of a lower alkyl, methyl, which produces a high-degree molecular chain configuration.